what's the deal with "refraction"?

why refraction looks so weird in ue4? is it some sort of simulated refraction since it must be expensive to calculate? I mean, a sphere must look ok, but when you make a window lets say and apply a refractive material, the refraction is actually a replication of the face you are looking at at a different angle. I mean, what? is this the normal refraction for flat surfaces in ue4? cause it doesn’t look good at all, I find myself turning it off every time.

am I doing something wrong?